Cumberland County Utilities Authority, Bridgeton, NJ

The Cumberland County Utilities Authority (CCUA) Wastewater Treatment Plant (WWTP) has served as a sewage treatment center since the late 1800's. In May of 1979 the CCUA opened a 7 MGD WWTP and today is the largest user of the Cohansey River Basin.

The plant is a secondary treatment design with, flow equalization, primary & secondary clarifiers, two 1.5 MGD aeration tanks, and sodium hypochlorite disinfection. Solids are processed by anaerobic digestion involving one primary digester and one two stage secondary digester.

The final disposal of sludge from the plant is by incineration used only at certain times of the year and by land application. Sludge residuals applied to land are tested to strict standards set forth by the NJDEP and EPA, once tested and approved are classified as beneficial biosolids. The CCUA applies biosolids with a specially designed truck through subsurface injection. Farms use CCUA biosolids do so for their effective soil conditioning benefit in growing sod, nursery stock, and grains.

The NJDEP biosolids land application program is in some ways more stringent than the federal requirements set by the EPA.
Biosolids can only be applied through the strict guidelines set forth under the direction of the New Jersey Department of Agriculture's Agricultural Management practices and right-to-farm requirements.

Application require's individual site review and official documentation from the NJDEP which must state Land Application Management Approval.

Additional requirements can be added at any time by the department to a permit based on review of the residuals being applied to the land.

Pictured is the CCUA specially designed truck, subsurface injecting Biosolids. Due to the success of the Biosolids program and BAE, the CCUA received the EPA National First Place Award for "The Beneficial Reuse of Biosolids".

The CCUA began using BAE in their primary anaerobic digester because they were having difficulty maintaining the minimum volatile solids destruction (VSD) of 38% required by the NJDEP for land applying sludge.

These problems also affected the methane production within the digester, causing the plant to rely on their local natural gas supplier to provide energy for operating the boilers to heat the digester as well as the boilers responsible for heating the administration building.

Methane production from anaerobic digestion requires proper pH and reliable organic matter to promote maximum methane production. When these two issue were examined it appeared that both were in good order.

The boilers were checked and temperature of the biomass in the digester was monitored. This was done because methane producing bacteria are extremely sensitive to temperature change and a swing of 20°F can cause a 50% loss in methane production and as little as a 5°F swing can inhibit methane formers enough to cause acid accumulation, foul odor, and possible digester failure.

750,000 Gallon Primary Digester

After completing several evaluations of the primary digester it became evident that there was a breakdown in the two-part process involved in the anaerobic digestion.

It appeared from the operation of the digester that the first phase of digestion was taking place. The biomass was being broken down into simple organic compounds by the acid-forming bacteria.

It was the second phase that was having difficulty responding to the environment. It was in this phase that the acid forming bacteria seemed to dominate the methane-forming bacteria,
causing a break down in methane production and creating a foul acid type odor.

BAE was added to the digester at the rate of 3 gallons per day. Within 90 days the odor was eliminated and methane production was at its maximum production, creating more gas then the demand required; the digester had recorded VSD levels as high as 62% and began to level off at a VSD of 55%.

BAE had clearly demonstrated that a balance between the acid formers and methane formers had been created and a stimulating effect was taking place within the primary digester, improving the performance of the two-stage secondary digester. Dewatering by the plants centrifuge machine improved, receiving digested sludge as high as 6% creating a dewatered cake at 25 to 28%.

The CCUA made the decision to change the dewatering process from centrifuge to gravity belt thickening. This process required polymers to be added at the influent of the gravity belt and some of this material worked its way into the primary digester.

Polymers used in this operation were toxic to the methane formers, causing a loss of gas and excess volatile fatty acids and the odors associated with them. BAE was increased to compensate for the problem; within 120 days the problem was eliminated and today the primary digester operates at a VSD of 55 and higher and the rate of BAE treating the digester has been reduced to 2.8 gallons per day.

Because of the success experienced in the primary digester it was decided to treat the aeration tanks with BAE as well.

From the day the plant went on line the organic loading averaged 675 mg/l BOD and for several years it experienced high levels of TSS and BOD in the effluent; many remedies had been tried to eliminate the problem.

BAE was added to each 1.5 MG aeration tank at the rate of 1.5 gallons. Within 30 days the TSS BOD levels began drop; now both are both below 10 mg/l daily.

As we have seen many times before from the use of BAE the biomass activity increases within the aeration tank, and mixed liquor levels are now lower then ever before. As a result of this efficiency from the addition of BAE, the CCUA has taken one of it's 1.5 MG aeration tanks out service.

Pictured is one of two 1.5 MG aeration tanks with air supplied by fine bubbling diffusion. Following six months of treatment with BAE to both aeration tanks, one of the two tanks was removed from service.

Stimulation of microbial growth due to the treatment of BAE in anaerobic and aerobic environments has been shown again. These benefits help WWT and have greatly contributed to the clean up of our waterways.

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